Rapid load testing machine



NOV. 27, 1951 D s, WOOD RAPID LOAD TESTING MACHINE 2 SHEETS-SHEET lFiled Feb, 16, 1949 JNVENTOR. mwa 5. wooo HNO Nov. 27, 1951 D. s. woonRAPID LOAD TESTING MACHINE Filed Feb. 16, 1949 2 SHEETS-SHEET 2 IN V ENTOR.

A77 Tae/VEY Patented Nov. 27, 1951 the United States of America asvrepresented by the Secretary of the. Air Force `Appli@ation February 1This invention relates to a load testing machine and is particularlyadapted'-v for applying a predetermined and cntrolied. tensiley load ata desired rate to a test specimen.

l Inthe operation ofconventinal hydraulic tensile testing machines therate atwhich load is appliedto the test specimen can only be controlledby continuous manual adjustment of the machine. It therefore an objectof this invention. to provide a machine of this general class withmeanswhereliy the period of time within which the desired load isaccepted by the specimen `may be predetermined and automaticallycontrolled to the end that the loading of materials as occur in actualuse may be more closely simulated.

It` is particularlyan object of this invention to provide a means ofapplying a load within a periodof time; which is much shorter than thelength of timerequiredto apply a load in a onventidnal testing machine.

Another object is to, provide` a tensile load testing machine in which agreater number of specimens may.- be tested in a given time than isusual in common practice. l

Qther objects and advantages may be discovered by inspection of thefollowing descriptionand drawings, wherein:

Fig. 1 is a longitudinal vertical axial section through myY improvedtensile load testing, machineig`f'2 is an axially-#transverse sectiontaken on the line 2-2 of Fig'. 1.

Eig. 3 is a section taken at 3-3 of. Fig. 1 through thep'iston rod.v

Eig; e. is a section taken at 4--4 of Fig. l showingthecam mechanism forcontrolling the rate of application of the load.

Lilie reference. characters refer toy like parts throughout the severalviews.

Referring more particularlyA to Fig. 1, the main frame l of the machineconsists` of a cylindrical portion l2 with integral base I 4 and ribsI-B, the base L44 being provided with supporting legs I8 integraltherewith or attached thereto -in any suitable manner.

At its upper end the frame I0 is bored at 20 to receive a large flangedcylinder 22 which is secured in the frame by screws 24.

At its upper end the cylinder 22 is closed by a flanged cylinder head 28which is secured to the cylinder 22 by screws 30. Seal rings 32 areprovided to prevent leakage between the cylinder and head.

Extending upwardly from the tcp of the flanged P" *A cylinder head 28 isa pair of pillars 34; with a 55: ,A sma-llpl nger; is-'s able ina crossbeam 36' held` to the topv of the pillars by screws 38. The cross beam36` is centrally bored at 411i andI counterbored at- 42 to receive asplit bushing M whereby the enlarged end 46 of a test specimen t8; isheld for application. of load'. A cos x to the.'underside l -priretmaken: be

2v Y threaded' bushing. incorporating a spherical seat and a matchingspherical seat in the cross beam Siicouldalso be.used. A

SlidableinA thebre il,l off the cylinder 22 is@ "Dl' il'f2"'whichdividestlie space inside the' 2 2 into' an upper chamberPipejs and 5i' com: n'iunicat' respectively with chambers 54 and 5Ewhereby'an expisibl'e fluid may be brought intoi the chamber 54 andannoncompressible ui'dinto' -the chamber 561 A c onijentionial pressureregu'- letting' unitA 5'3A is provided whereby, when the pis-'- tg'rlfldescends sli'eh- 1r durmg the' operation of' taRgf a liest; the pressure'in chamber 5,4 Will remain unfirm throughout the test2 A,ccriviei'i-` 1'tional' two-wai valve 591s provided for control# 1mg, the amount er.circdmpressible fluid chamber 56. A pistn rou' 58' xtendsupwardy andhas sliding' bearing ijn a "ce h" rr zsf. Sfe'al rings. sa

Een the piston rod-5c anic the hub 6.0, seairings 64 pistoii; Y c

At its upper end the piston. .lIQd' 5'8' is bored as, at 470.'and-cqunterboredas abili!" t receive a vsplitbushin'sf 4t( wh jeby theenlarged endg 461 of ai est.. spannen is; leed. spia sus 44;" rsinverted bis me' ifncorpratmgi a spneriear Seat cours zii-scbeiuseciinpiace,orluli;L

Beier-'miie meer edge; of the bushing 44* the' Opening 6&- iS' 'shapedFi ,r spia bushing, v41V may' ce' gaat n arf-spina me. egn= here forapplicate, n or ergert end'tsf or the test, specimen ra wir-ena'spe'cirnenisbfeing,inserted; i

C o'ncentrically held', between the lowr Vend' Qf frame part [2 oi the"frame I0i's11 a.1ing' lllwh supports a, series of circ, erenti'alflyspaced d pending ribs. 12W winch cbm/erge at the: weer end* 15yringsiifs re. prev/ideare me: edges or meri' 'sum1 menttherein;

berY 9i!l which -i's main-tamed coaxial withthe pi ton-Tais Iby .trieplate 19e is 'recessed iin' the base I4 and fastenedviitir-screws'dr'lile' means;

beine, provided' f'oir thl 3 order that the saturer tirera-'- f the base|4 by screws |00, a T-shaped tongue |02 on the top of the housing ttinginto a T-V shaped groove v|04,inthe.bottom ofthe base |4. A cam |06 isalso provided with a T-shaped tongue |08 in its upper edge whichslidably fitsy the T-shaped groove |04 in the bottom of the base I2, thegroove being also carried/through asffegas the bottom of the plate 96,whereby the cam |06 knob ||2 is slidable in an opening in the wall of YY the housing 98 and has itslinner end fixed in the cam, whereby the`cam may be moved back manually to its normal position as shown insection inFig.1.`

In the top edge of the cam |06 'a'plunger operating groove is formed,the right-hand half ||4' of the groovebeing relatively shallow and theleft-hand half ||6 'being' deeper, the two parts of the groovebeingjoined together by a sloping portion ||8. The round plunger 92 isflattened on the sides as at '|20 to fit the groove ||4, ||6 freely, theheel |22 of the plunger 92 being sloped to correspond to' the slope |8of the groove. The vunderside of the cam |06 has two depending portions|24'and |26'joined by a semicircle |28 the center of which'is on avertical line which bisects the slopingv portion IIB of the cam groove.The purpose of this construction will be apparent when coactingstructure is hereinafter described.

The cam operating drum |30 is rotatable by a shaft |32 which has bearingin a' hub |34 of the cam housing 98. A pulley |36 is'fast on the shaft|32' and is adapted to be driven through a variable speed motor |35 anda V belt |31 or other suitable means. I

A coaxial opening |38 andan axially parallel opening |40 are provided inthe drum A|30 for respectively receiving the 'plungers |42 and |44slidably. .'A light spring |46 and a relatively heavy'spring |48respectively'urge the plungers |42 and |44 toward Vthe outer end `ofthevdrum. Both plungers |42 and |44 are'annularl'y'grooved as at |50 and|52,'th'e sides of the grooves 'being beveled. .A bevel ended lockingplug |54 is slidable in a'radial opening in thedruim' |30, the axes ofthe plungers'l42 and, |44 and, that of the locking plug |54 being all inthe same plane. The locking plug |54 isofsuch' length that when one endof the plugV isfat the bottom of one of the annular grooves, the otherend of the plug is even with the top of the other annular groove.

Plunger |42 has a push button'end |56I`extending through'thefront coverV|58 of the cam housing 98, the push button portion being smaller thanthe plunger proper'whereby the shoulder |60 thereby formed on theplunger |42 limits' axial 4movement ofthe plunger 'byithe spring |46.The other plunger |44 is reduced in diameter at its forward end as at|62, the reduced portion being of such length that when the plunger 44is inthe retracted state shown' in Fig. 2, the forward end`of theplunger just clears the cam |06.

Means for returning the plungerY 44 to the rtracted state comprises asmall vpush rod |64 Y radially equidistant with the plunger'l 44 fromthe axis of the drum |30 andwa lever |66 hinged at |68 for forcing thepush rod inwardly. VA light spring |10 held in place by .across pin |12is provided for returning the push rod to its home position. A s lameans for aligning the plunger |44 with the push rod |64 when it isdesired to returnthe plunger |44 to the retracted position an arrow |14on the pulley |36 maybealigned with an appropriately placed arrow |16 onthe frame part I6.

split bushing 44 may be placed around it. By

lowering the large piston 52 back to the position shown in Fig. 1, thespecimen will be in proper position as shown for taking the test.

If the cam |06 is not already in the position shown in section in Fig.l, it may be brought to this position by pulling out the rod ||0, and ifthe plunger |44 is not already in the retracted position shown in Fig.2, it may be returned to the retracted position by aligning the arrows|14 and |16 then pulling the lever |66 in the direction of the arrow|18.

Compressed air or other expansible'uid is now let into the upper chamberthrough the pipe 55, the noncompressible fluid in the lower chamber 56,which may be a viscous fluid such as glycerin, being increasedsimultaneously in Aorder to maintain substantially zero tension in thespecimen 48.

The power source which rotates the pulley |36 is started and brought toa selected speed and the push button |56 is depressed, whereupon theVheavy spring |48 forces the locking plug |54 out of the groove |52 andinto the groove |50 which holds the push button |56 in the pressed inposition but permits the plunger |44 to move axially forward whereby,upon rotation, it wil1 engage the cam surface |26 whereby the cam |06will be moved to the position shown in phantom in the right side of thecam housing. When the cam has been so moved, the drum |30 may continuerotation without doing further work.

When the cam |06 in moving from left to right, has reached substantiallythe mid-point of its travel, the small plunger 92 rides olf the highportion ||4 of the cam down the incline I|8 and on to the low portion||6. It is noted that just as the small plunger 92 is riding down theinoline ||8, the plunger |44 issubstantially at top center and itsdriving end |62 is between the surfaces |24 and |26 whereby the downwardforce on the small plunger 92 may not cause the cam to overrun theplunger end |62 which is driving it.

When the small plunger 92 rides down the incline ||8 the support for thelower piston 86 is removed. Since the expansible iuid is still exertingits pressure on the top of the large piston 52, the test specimen 48 issubjected to arsudden load, the extent of the load being determined bythe pressure of the expansible fluid and the suddenness beingcontrollable'by varying the rotative speed of the drum'l 30 and/or theslope I8 of the cam. During the slight movement of the large piston 52,the pressure in the chamber 54 throughout the piston movement ismaintained at the value to which the pressure regulating unit 53 isadjusted. The cell 82 reduces to a minimum any oscillations of thenoncompres-...V1

sible fluid in chamber 56. Due to the damping effect overtravel oroscillations of the large piston 52 is eliminated.

After applying the test to one specimen, the machine is readied for thenext by (1) substituting a new specimen for the tested one; (2)returning the cam |65 with the rod Ill; (3) aligning the arrows |74 and|15; (4) operating the lever |55; (5) starting the motor |35 whichrotates the pulley |36; and (6) pressing in the push rod |56. g

Having shown and described one embodiment of my invention wherein theobjects set forth are attained, I claim:

l. A testing machine for rapidly applying a predetermined load to a testspecimen at a predetermined rate comprising a machine frame, means onsaid frame for removably securing one end of the test specimen thereto,a work cylinder having a rst piston therein, a piston rod connected tothe rst piston and having its other end adapted to be removably securedto the test specimen, means connected to said cylinder to apply apredetermined fluid pressure to one side of said rst piston, a secondpiston in said cylinder, the space in said cylinder between said pistonsbeing filled with liquid, and a mechanism comprising means operativewhen in its home position to hold said second piston against movementwhereby the liquid trapped between said pistons prevents movement ofsaid rst piston and application of load to the test specimen, andmovable at a predetermined rate through a predetermined distance tocause movement of the second piston at a predetermined rate in adirection such that the predetermined fluid pressure causes movement andapplication of load to the first piston at a rate proportional to therate of movement of the second piston.

2. The structure as claimed in claim 1, in which fluid flow restrictingmeans are positioned in said work cylinder in the space between saidlirst and second pistons to damp to movement of iluid therebetween andprevent oscillations of the load applied to said test specimen.

3. A machine for applying a predetermined tensile load to a testspecimen in a controlled period of time, which comprises an elongatedframework having a cylindrical opening therethrough, a cylinder head forclosing one end of said opening, two spaced apart pistons slidable insaid opening, the rst near said cylinder head thereby forming a firstchamber for an expansible fluid under pressure and the second near theother end of said cylindrical opening thereby forming a second chamberbetween said pistons for a noncompressible fluid, means to control thepressure of said expansible iluid, means to control the volume of saidnoncompressible fluid, means carried by said framework for holding oneend of a tensile test specimen, means for joining the other end of saidtensile test specimen to said lirst piston, a cam slidable transverselyof the cylinder axis at the end of the cylindrical opening near saidsecond piston, said cam having a high and a low surface connected by aslope from one surface to the other, means extending from said secondpiston to said cam normally supporting said piston on the high surfaceof said cam against the pressure in said first chamber and means forcontrolling the speed at which said extending means slides down saidslope so that the pressure on said second piston is transferred down theslope from the high surface down to the low surface in a predeterminedperiod of time.

4. Claim 3 wherein the said means for sliding said cam transverselycomprises a rib depending from the underside of said sliding cam, saidrib having a slot in the form of an inverted U intermediate its ends, arotatable drum, a coaxial plunger having its forward end extending fromsaid drum ior engagement with said slot and an axially parallel drumplunger having its forward end adapted for engagement with said slot,both plungers having a bevel sided annular groove intermediate the ends,and both slidable in openings in said drum, a coil spring in back ofeach plunger urging said plungers forwardly out of their openings insaid drum, a radially disposed plunger retaining plug having beveledends for entry into said bevel sided annular grooves, the plug andplungers all having their axes in the same plane, the length of the plugbeing such that when one beveled end is all the way in one annulargroove the other beveled end is all the way out of the other annulargroove, push button means for pressing the coaxial plunger in until itsannular groove aligns with said plug, and means including a lever forpressing said axially parallel drum plunger in until its annular groovealigns with said plug.

5. Claim 4 with a housing open at the front end surrounding said cam anddrum, a lid for said housing, an axially parallel lid plunger slidablein an opening in said lid located the same distance from the axis of thedrum as the axially parallel plunger in the drum, means to indicate whenthe axis of the axially parallel plunger in the lid and the axis of theaxially parallel plunger in the drum are coincident, the said levermeans being operative also to press said axially parallel lid plungeragainst said axially parallel drum plunger until the bevelled end of theradially disposed plunger retaining plug is in alignment with theannular groove in the axially parallel drum plunger.

6. In a tensile testing machine, a frame having a main cylindrical boresubstantially closed at both ends but with a small bore emanating fromeach end, a piston rod slidable in one end bore, means on said frame forfastening one end of a test specimen, means on the outer end of saidpiston rod for fastening the other end of said test specimen, a mainpiston fast on the inner end of said piston rod and positioned to leavea gas pressure chamber between said main piston and the said one endbore, a relatively small piston in the other end bore thereby forming aliquid pressure chamber between said main piston and the said other endbore, means to control the pressure in said gas pressure chamber, meansto control the volume of said liquid pressure chamber, and cam meansmovably mounted at the outer end of said relatively small piston forcontrolling the rate of outward movement of said relatively smallpiston.

DAVID S. WOOD.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 570,970 Tomkins Nov. 10, 18962,081,599 Peters May 25, 1937 2,191,282 Lewis Feb. 20, 1940 2,354,562Webb July 25, 1944 2,386,989 Summers v Oct. 16, 1945 2,474,235 Dresseret al June 28, 1949

